Feeling bad - is it the bonk?

[axel_knutt]

I've never ground to a complete standstill on the bike, even when I ran out of food, but there were a few occasions when I felt very nauseous an hour or two after finishing, and the feeling went after eating. Generally, if I'm riding more than 30 miles I try to stop every hour and eat about 250kcals. I don't get hung up on eating specific foodstuffs that aren't going to be available at any old village shop in the middle of nowhere, or anything that's expensive.

[Cowsham]

I've only had the feeling of total exhaustion 25 miles from camp after 80 miles of mountain bike territory and no shops I could find until a passing cyclist who knew the area was able to tell me which direction to go to find one that was open after 6pm. Desperately needed water ( and food ) I'd run completely out for about 3 hours and that's quite scary.

When I did get to my tent in darkness I felt close to death and had terrible leg cramps all night. ( Aged about 56 then )

[Audax67]

Bonk is simply hypoglycaemia, i.e. your blood sugar level has dropped below the normal range.
...

I don't think that it is. But if you have some evidence...

... and of course it's much much easier to measure plasma glucose concentration it used to be...

Jonathan

Nonetheless I'm not going to schlepp my BG meter along on rides. I can offer this, though: after I got my first stent, the hospital dieti-chienne told me to stop putting sugar in my bottles and avoid sugary stuff at controls. I tried it for one ride, and had such a vile case of bonk that I thought I was having a heart attack: no energy, trembling, ready to fall over sideways. I ate one of the sugary bars she'd told me to leave behind and I was fine in a few minutes.

[Audax67]

Bonk is simply hypoglycaemia, i.e. your blood sugar level has dropped below the normal range.
...

I don't think that it is. But if you have some evidence...

... and of course it's much much easier to measure plasma glucose concentration it used to be...

Jonathan

The OP links to Trainer Road an esteemed training app it says 'Bonking is a dreaded experience and occurs when the body becomes functionally depleted of glycogen.'

What do you think it is ?

Glycogen is simply a storage form of glucose, and has to be converted to glucose before it can be used. You can find it in the muscles or in the liver.

[peetee]

I'd definitely include neuroglycopaenia in the possible causes for that constellation of symptoms:
https://en.wikipedia.org/wiki/Neuroglycopenia

Initial investigations would include measuring plasma glucose and serum insulin and C-peptide.

Jonathan

Thanks for that. I've never had any medical attention directed towards it. For me it was just a case of being adequately stocked with energy gels, just in case.

[mattheus]

I can offer this, though: after I got my first stent, the hospital dieti-chienne told me to stop putting sugar in my bottles and avoid sugary stuff at controls. I tried it for one ride, and had such a vile case of bonk that I thought I was having a heart attack: no energy, trembling, ready to fall over sideways. I ate one of the sugary bars she'd told me to leave behind and I was fine in a few minutes.

Probably the biggest reason for this happening is you've effectively hooked your body on high-sugar intake.

Just like smokers who cough through the waking hour until their first fag. They say it makes them feel soooo much better!

[Jdsk]

I'd definitely include neuroglycopaenia in the possible causes for that constellation of symptoms:
https://en.wikipedia.org/wiki/Neuroglycopenia

Initial investigations would include measuring plasma glucose and serum insulin and C-peptide.

Thanks for that. I've never had any medical attention directed towards it. For me it was just a case of being adequately stocked with energy gels, just in case.

Very interesting that it sometimes occurred without serious exercise. And that it doesn't happen any more.

Jonathan

[Audax67]

I can offer this, though: after I got my first stent, the hospital dieti-chienne told me to stop putting sugar in my bottles and avoid sugary stuff at controls. I tried it for one ride, and had such a vile case of bonk that I thought I was having a heart attack: no energy, trembling, ready to fall over sideways. I ate one of the sugary bars she'd told me to leave behind and I was fine in a few minutes.

Probably the biggest reason for this happening is you've effectively hooked your body on high-sugar intake.

Just like smokers who cough through the waking hour until their first fag. They say it makes them feel soooo much better!

I've been diabetic for 40 years. My standard medication reduces sugar uptake from the gut, burns muscle glycogen all the time and depresses the release of glycogen from the liver. If I cut stop taking it, it takes 4 days to be eliminated, so on every ride a deal of the sugar I consume remains in the gut. When I ride without sugar intake I depress my blood sugar & the remaining muscle glycogen in about half an hour. Not recommended.

For added entertainment, the sugar that stays in the gut is fermented by intestinal bacteria so that faeces are reduced to a kind of high-pressure expanding foam, sometimes posing a swift and severe sphinctoral challenge. I can avoid this by totally abstaining from sugar but when I'm on the bike the outcome of that is gloomy.

The sugar in my bottles is Isostar, BTW, not the stuff people ruin their coffee with.

[axel_knutt]

faeces are reduced to a kind of high-pressure expanding foam

I used to get that quite a lot back in my cycling days, but I haven't had it for years.

[mattheus]

I can offer this, though: after I got my first stent, the hospital dieti-chienne told me to stop putting sugar in my bottles and avoid sugary stuff at controls. I tried it for one ride, and had such a vile case of bonk that I thought I was having a heart attack: no energy, trembling, ready to fall over sideways. I ate one of the sugary bars she'd told me to leave behind and I was fine in a few minutes.

Probably the biggest reason for this happening is you've effectively hooked your body on high-sugar intake.

Just like smokers who cough through the waking hour until their first fag. They say it makes them feel soooo much better!

I've been diabetic for 40 years. My standard medication reduces sugar uptake from the gut, burns muscle glycogen all the time and depresses the release of glycogen from the liver. If I cut stop taking it, it takes 4 days to be eliminated, so on every ride a deal of the sugar I consume remains in the gut. When I ride without sugar intake I depress my blood sugar & the remaining muscle glycogen in about half an hour. Not recommended.

Oh dear - sorry to hear about that :-/

You fooled me with the "stent-talk". I didn't twig that - like the OP - you hadn't mentioned your diabetes.
SO ... when I looked into all this sugar/exercise business, I wasn't considering diabetes, so this is just off the top of my head, but:
the whole point of fasted training, low-carb diets etc (even keto for the hard-core!) is that you need much reduced, minimal sugar absorption from the gut. I can ride quite hard for hours on an empty stomach, and ride 4 days with 7h sleep just on fats/protein.

A quick google - a VERY quick google - suggests fasted training works well with Type 1 Diabetes.

[Audax67]

Probably the biggest reason for this happening is you've effectively hooked your body on high-sugar intake.

Just like smokers who cough through the waking hour until their first fag. They say it makes them feel soooo much better!

I've been diabetic for 40 years. My standard medication reduces sugar uptake from the gut, burns muscle glycogen all the time and depresses the release of glycogen from the liver. If I cut stop taking it, it takes 4 days to be eliminated, so on every ride a deal of the sugar I consume remains in the gut. When I ride without sugar intake I depress my blood sugar & the remaining muscle glycogen in about half an hour. Not recommended.

Oh dear - sorry to hear about that :-/

You fooled me with the "stent-talk". I didn't twig that - like the OP - you hadn't mentioned your diabetes.
SO ... when I looked into all this sugar/exercise business, I wasn't considering diabetes, so this is just off the top of my head, but:
the whole point of fasted training, low-carb diets etc (even keto for the hard-core!) is that you need much reduced, minimal sugar absorption from the gut. I can ride quite hard for hours on an empty stomach, and ride 4 days with 7h sleep just on fats/protein.

A quick google - a VERY quick google - suggests fasted training works well with Type 1 Diabetes.

No sweat. I'm a Type 2 so quite different from a T1. My current régime works pretty well, apart from the odd panicky scamper into the undergrowth/nearest patisserie, and I wouldn't care to try a shift to fat-burning or some such.

[Pinhead]

Thanks all

[cycle tramp]

Different folk have/need different fuelling strategies, but if you're doing work you need fuel. But it doesn't have to be special super-whizzy expensive sports-nutritionist and elite athlete endorsed fuel... World champion, hour record holder and famous outside-the-box thinker Graeme Obree was a firm believer in the power of... jam sandwiches! (the jam gives you quick release carbs while the bread gives you slower release carbs).

Exec summary: on-the-go fuelling is good, starting off fuelled is good, you don't need expensive "sport nutrition" products and indeed alternatives may well be nicer and cheaper. And fuelling is a great excuse for a café stop!

Pete.

Absolutely- during the times when I was doing 'moving on tours', I'd be drinking a pint of milk a day and having a couple of pasties....

..one of the things which haven't been mentioned, is cycling more often. Certainly during some moving on tours, it wasn't unusual for everyone to have a mid day meal by mile 30..... and as the days wore on and everyone's body became used to the physical exercise, people wouldn't stop for lunch, but knock out the 60 or so miles, with minimal breaks in between and then eat properly in the mid afternoon..

[Cowsham]

Good info here -- I'll need it -- only about a month to go before my cycle trip. First few days are up near the 100 milers.

[Vorpal]

A bit late to the game, but we've had a few threads before...
on the bonk:
viewtopic.php?p=793659#p793659

nutrition for cycling
viewtopic.php?p=1766312#p1766312

the bonk & diabetes
viewtopic.php?t=123562